Acid-Base Physio Flashcards
Maintenance of proper pH? (3)
- Intr/extracellular buffer of body fluid
- Respiratory mechanics (CO2)
- Renal mech (excrete H+-reabsorb & produce HCO3-)
normal pH of blood
7.4
acid classifications in humans; exist as one of two forms:
volitle acids: can be breathed out (CO2)
Fixed acids: produced by metabolism
sulfuric (protein metabolism)
lactic
ingested acidsacids assumed to dissociate completely when in aqueous solution
strong
acids dissociate only slightly in aqueous solution–majority of molecules remain undissociated
weak acid/ conjugate bases
chemicals and proteins that can absorb free H+ or donate a H+, so pH change only minimally
buffer
buffer capacity is critical– otherwise we would see…
wild changes in tissue pH (locally and systemically w/ normal activities)
pH =
H+ concentration
pH = -log[H+}
point at which, for given acid or base, equilibrium is reached btwn the dissociated form ({H+} & {A-}) and the associated form ({HA})
K – Equilibrium Constant
K=
[HA]
K for HCL will be
a huge number
pK for acid is midpoint btwn
HA and A-
At equal concentrations [A] and [HA], pH =
pK
curve plotted for pH of solution w/ buffer, while adding acid or base will be ________ in shape
sigmoidal–additions will look flat at high and low end
slide 7
3 main buffers in extra cellular fluid ECF
- bicarbonate HCO3-
- inorganic phosphate
- plasma proteins (trade Ca++ for H+)
HCO3- (pK, normal conc.?)
Most important buffer in humans
pK=6.1
18-28 mEq/L
albumin has ____ charge so neutralized when add ____
negative,
H+
inorganic phosphate pK
6.8
*in blood: H+ + HCO3- –> <–
imp equation for other things
H2CO3 –>Ca++ takes spots on albumin–> hypocalcemia (low free calcium in blood) –> CARPAL PEDAL SPASM
2 ICF buffers
- organic phosphates
2. proteins (HEMOGLOBIN, deoxyhemoglobin)
treatment for Carpal Pedal Spasm
rebreath CO2 out of paper bag
Renal mechanisms in acid-base balance (buffer)
- reabsorption of filtered HCO3-
2. synthesize HCO3- ( for each H+ excreted, 1 HCO3- made)
kidneys excrete________, maintaining acid-base balance
- fixed acids
2. H+ as NH4+
pulmonary balance of acid/base is _________, maintains pH by varying _______ ________, which changes ______ and therefore pH
rapid,
minute ventilation,
PCO2
blood pH of less than 7.35 (^ in H+ or v in HCO3-)
acidemia/ acidosis
watch video on CO2 HCO3- H+ H2O relationship
renal mechanics of acid-base
disorder of pH greater than 7.45 from decreased H+ concentration
alkalemia/ alkalosis–secondary to ^ minute ventilation
Acidemic or Alkalemic disorders subdivided into: (2)
- Metabolic acid-base disturbances
2. Respiratory acid-base disturbances
Metabolic acid-base disturbances usually from
increased fixed acids, sometimes decrease in HCO3-
- ^ non-vol acid production
- decrease renal acid excretion
- dec renal HCO3- synthesis
- loss of alkali (HCO3-)
Respiratory acid-base disturbances from
disturbance in PCO2 from (respiratory acidosis vs. alkalosis)
fixed acids aka
nonvolatile acids
pH identifies disorder as acidemic or alkalemic,
PCO2 levels ID a ______ component to pathophys
HCO3- levels ID a _______ component to pathophys
respiratory,
metabolic
for each change in PCO2 of 10mm, pH will change by appx. ____ in _________ direction
0.08, appx 0.1
OPPOSITE
2 primary mechanisms used to maintain pH
- respiratory compensation–rapid PCO2 change(^ minute ventilation to exhale CO2)
- renal compensation–HCO3- and acid excretion
- pH 7.5 dx
will be one of these on exam–examples in ppt
low PCO2 or
high HCO3
*pH 7.28 dx
low HCO3- (bicarb) or
high PCO2
respiratory acidosis from
hypoventilation (3)
1. CNS problems (drugs, TBI, tumor, stroke) 2. Pulmonary disease states (COPD, asthma, pneumothor) 3. Neuromuscular disease (tetanus, botu, poison)
aspirin
salacilic acid–lower pH
respiratory alkalosis from
hyperventilition (6)
1. anxiety
2. hypoxia
3. pregnancy (^ estrogen)
4. High altitude (relative hypoxia)
5. sepsis
6. physiological response to metabolic acidosis ("metabolic acidosis w/ a respiratory compensation")
metabolic acidosis from (3)
- over-production of acid
a. diabetic keto-acidosis
b. lactic acidosis - decreased excretion of H+ (RENAL FAILURE)
- loss of HCO3- (GI or renal losses)
a measure of unmeasured anions (-)
anion gap
anion gap used to
refine the ddx of METABOLIC ACIDOSIS
measure of cation concentration vs. anion concentration
anion gap test
normal anion gap range
8-16
If bicarb is lost, body hold onto___ to lessen _____ ______
chloride,
anion gap
anion gap can be used to confirm _______ ________ or loss of _______
metabolic acidosis,
HCO3-
way of differentiating types of metabolic acidosis
anion gap ( i.e. too much acid vs. not enough bicarbinate) confirmatory of clinical findings (i.e. does pt have diarrhea?)
low anion gap indicative of
hypoalbuminemia
normal anion gap w/ acidosis indicative of
pt loss of HCO3-
if anion gap is increased indicative of
pt has “extra acid” in system
acid =
cation
